Added stripCloneAtts() method.
Renamed method to stripCloneAttrs()
Fixed false-negative attribute check bug.

The check now allows for "false" boolean attributes.
Return the clone
Built CS file
Merge branch 'master' into clone-attributes-fix
A more robust way to check if the model attribute exists

previously the clone attribute wouldn't get removed if set to `null` or
`undefined`.
Merge pull request #351 from adambiggs/clone-attributes-fix

Fix for #219